This invention relates to a method of making bags and relates more specifically to a method of forming the bottom of a bag of the automatic or self-opening satchel-bottom type.
The invention relates specifically to bags of the indicated type that comprise an outer sheet of paper and an inner liner of an impervious material such as a plastic (synthetic resin). In the conventional method of making bags of the indicated type, a tube is formed having an outer sheet of paper and an inner liner. The bottom end of the bag is formed into a diamond fold with a tab portion at one end thereof. After the diamond fold and the tab portion are sealed, the bottom of the bag is completed by folding over the tab portion onto a previously folded over diamond fold portion. However, this last step requires that the inner liner of the tab portion be adhered to the paper surface of the diamond fold. The adhering of the plastic liner material to the paper outer sheet material is difficult to achieve consistently.
In accordance with the method of the invention a part of the liner is removed during the bag making method so as to permit the application of adhesive to a part of the bag such that a paper contact is achieved between the tab portion and the diamond fold portion during the last step in the bag bottom formation. More specifically, during the formation of the tube from which the bag is made, a rectangular portion near the bottom edge of one side wall is not adhered together and a slit is formed in the liner in this rectangular area extending parallel to the bottom edge and spaced therefrom. In accordance with the method of the invention, the liner portion between the slit and the bottom edge of the bag is removed to provide a paper surface which can be adhered to the paper portion of the diamond fold when the bag bottom is completed. This permits a better adhesive bond to be achieved during the bottom formation of the bag since the bond is produced by paper-to-paper contact.